The Sound of External Loops

[glasman]

Here are a few graphs of loop (dlator) response. Those that have used the external (or internal) loop with their amps know they have the tendency to smooth out the smooth. Of course the connecting cable has a large effect on the response. But loop itself also has a large coloration effect on the tone (in a good way).

There is a lot of room for "tweaking" the recovery amps with respect to the feedback loop and miller compensation network.

Have fun.

Gary

[Bob-I]

Very nice work, but I'm not sure how this all relates to what I hear. It looks to me like the recovery side without the bright sw is a pretty normal guitar amp gain stage curve. Am I reading this wrong?

[glasman]

Hi Bob,

The point I was attempting to make was the roll-off in the recovery stage. From about 300 hz up there is a slow roll-off and corresponding phase change. I think this has a lot of the effect we hear in the softening of the top end with either a built in or external loop. The -3dB point is @ 12kHz.

The very top graph (rec @ 50%) slows this effect.

FWIW, the cables I used between the FFT and the Matchbox measured at

From analyzer to Matchbox : 126.47pf
From Output of Matchbox to analyzer : 172.12pf

The cables themselves could add a small amount to the roll-off. But measuring the response at the input to the recovery amp shows virtually no roll-off. Anyway, I was fingerprinting a new matchbox and thought I would share the results for those interested. For me it is a reference point. It gives me a starting point for improving the loop (response wise) for some other potential toys for studio use.

FWIW, I personally love the response of the bright switch on the send side. Looks like it was designed to drive 30 to 100 foot cable .

Clarification also. The 50% stated means the controls were at noon and the actual signal was about 15% of max for the stage.

Regards,
Gary